The present invention relates to a semiconductor device having a wiring layer consisting of a metal compound of a semiconductor material such as silicon, and to a method for manufacturing the same.
Silicon has a melting point which is as high as 1,400.degree. C. and therefore has a significantly high resistance to heat treatment under high temperatures as compared with aluminum which is conventionally used for electrodes or wiring materials. In a field effect transistor using silicon as the gate electrode material, the source and drain regions may be formed using the gate electrode as a mask. Therefore, the channel region is formed in self alignment with the gate electrode, so that the parasitic capacitance due to the superposition of the gate electrode with the source and drain regions may be reduced to the minimum. For this reason, silicon is considered to be a gate electrode material suitable for a field effect transistor which is required to operate at a high speed. However, a silicon layer, particularly, a polycrystalline silicon layer generally used for a gate electrode has a high resistance. For example, an n-type polycrystalline silicon layer of 3,000 .ANG. thickness has a sheet resistance of about 20 .OMEGA./.quadrature.. If the extending part of such a gate electrode is used as wiring, delay in signal transmission due to this high resistance impairs high speed operation of the device.
In view of this, it has been recently proposed to use silicides of metals such as Mo, Pt, and Ta for the gate electrode material in place of silicon. The layers of these metal silicides have resistances which are about 1/10 that of the polycrystalline silicon layer as described above. These metal silicides are also stable against heat treatment at high temperatures. Therefore, if these metal silicides are used for the gate electrodes, similar effects as those obtainable with the polycrystalline silicon layer may be obtained while simultaneously preventing an undesirable increase in the resistance of the gate electrode wiring. Furthermore, since these metal silicides are resistant to acids, they may be rinsed with sulfuric acid, nitric acid, hydrochloric acid or the like. In other words, these metal silicides may be handled in the similar manner as in the case of polycrystalline silicon in the manufacturing steps of the semiconductor device.
However, the metal silicide layers have coefficients of thermal expansion which significantly deviate from that of a semiconductor substrate of silicon or the like. For this reason, many interface levels are established by the residual distortion on the surface of the semiconductor substrate below the gate oxide film after heat treatment. This impairs the characteristics of the device. Furthermore, mobile ions in the gate oxide film below the metal silicide film are hard to getter.
In addition to this, the metal silicides have another problem of hard adhesion with semiconductor layer. For this reason, a good ohmic contact may not be obtained between a wiring of a metal silicide film and an element region formed on a semiconductor substrate. This problem is encountered in bipolar semiconductor devices as well as field effect semiconductor devices as long as a metal silicide is used as a wiring material.